# Talk:Functor hierarchy proposal

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Um, it would be good if it was something like:

class (Idiom f) => Monad f where fmap f m = m >>= return . f -- or ap . return ? ap mf mv = mf >>= \f -> mv >>= \v -> return $ f v (>>=) :: f a -> (a -> f b) -> f b

Or am I missing the point?

Serhei 15:24, 29 January 2006 (UTC)

- You can't put defaults for one class in another. Though that could be another proposal. —Ashley Y 21:02, 29 January 2006 (UTC)

- Wasn't this part of John Meacham's class system proposal? What happend to this? -- Wolfgang Jeltsch 19:25, 2 February 2006 (UTC)

<*>

ap

<*>

<*

`ap`

sequence

sequence_

mapM

mapM_

Applicative

Monad

Data.FunctorM.FunctorM

Applicative

I think it makes sense to take return out of Applicative. Either into a separate step between Functor and Applicative, or into a new class altogether:

class Boxable f where return :: a -> f a class (Functor f, Boxable f) => Applicative f where ...

But maybe this is just overengineering.

Twanvl 21:46, 15 January 2007 (UTC)